Device for atomizing melts

ABSTRACT

A device for atomizing melts, in particular liquid slags, includes a tundish intended to receive the melts and an atomizer head arranged in or on the outlet opening, A cooling chamber for the atomized melt is connected to the atomizer head. The atomizer head is designed as a hot cyclone running into the cooling chamber. Burners and/or propellant gas nozzles are connected to the hot cyclone.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a device for atomizing melts, in particular liquid slags, including a tundish intended to receive the melts and an atomizer head arranged in or on the outlet opening, a cooling chamber for the atomized melt being connected to the atomizer head.

[0003] 2. Prior Art

[0004] To granulate and comminute liquid slags, it has already been proposed to eject the same into granulation chambers by the aid of vapor or a propellant gas, further comminution subsequently being feasible also in jet mills using propellant gas jets. Departing from usual slag bath temperatures of molten slags of between 1400° C. and 1600° C., the relatively high temperature difference prevailing between a propellant gas jet and the liquid slag entails the risk of the formation of more or less large agglomerates as well as the danger of thread formation, which would consequently increase communication expenses and considerably reduce the cooling speed.

[0005] In AT-407 247, it has already been proposed to eject a melt from a melt tundish by the aid of a fluid under pressure with, in particular, pressure gas, vapor or pressure water having been pressed in from the tundish in the direction of the slag outlet. In such a configuration, the outlet from the slag tundish calls for special measures to prevent the outlet opening from freezing, and it was, therefore, suggested to lower a height-adjustable weir tube into the tundish in the region of the slag outlet in order to enable the control of the respectively outflowing amount, the propellant gas jet being introduced coaxially with the axis of the outlet opening and the tundish outlet running directly into the cooling chamber. Such an atomizer head designed as a nozzle into which the jet of a propellant gas lance coaxially runs, as a rule, calls for the use of highly superheated vapor in order to prevent the opening from growing together, high demands being set also on the refractory material as a function of the composition of the melt and, in particular, at an elevated iron oxide content of the melt. The same holds for the configuration of the height-adjustable weir tube, which is subjected to high wear in the event of aggressive melts and, therefore, requires a complex control for the correct adjustment of the height level of the weir tube. Besides such an atomizer head configuration in the form of an outlet nozzle from a slag tundish, other configurations may be taken, for instance, from AT-406 954 B, where the liquid slag is sucked into an expansion chamber being under a negative pressure and is conveyed into the cooling zone by the aid of a propellant jet.

[0006] AT-405 511 describes a method for granulating and comminuting molten material, in which liquid slag in the free fall is powered with pressure water jets, whereupon the solidified and granulated slag is conducted through a pneumatic conveying duct and a distributor together with the vapor formed. The thus distributed material may be immediately comminuted further in a jet mill. The basic procedures occurring during the granulation and communication of molten materials by feeding vapor to the same have already been described also in EP-683 824 B1, where a mixing chamber is provided, into which water, water vapor and/or air-water mixtures are nozzled, whereupon the evaporated water is ejected through a diffuser along with the solidified material. In such a configuration, the atomizer head is designed as a mixing chamber followed by a diffuser, whereby molten slag may be supplied from a suitable reservoir or tundish also in that case.

[0007] In AT-407 152 B, a solid material is melted in a melting cyclone, wherein a cooling chamber is directly connected to the melting cyclone that is closeable in a pressure-tight manner, which cooling chamber must subsequently be maintained under a pressure lower than that of the melting cyclone in order to enable the material to leave the melting cyclone and enter the cooling chamber. Since the melt heat required for such a method must be generated in the melting cyclone, a high amount of gas will be produced in the melting cyclone during the combustion of fuels, which necessitates subsequent purification that is accordingly cumbersome. Such a method may be controlled only to the extent at which the respective melt heat is provided as required, so that, in particular, a reduction of the produced gas amount and an adjustment to the desired cooling conditions cannot be achieved in the context of a melting cyclone of this type.

SUMMARY OF THE INVENTION

[0008] The invention aims to provide a device of the initially defined kind, in which the enthalpy of molten slags can be utilized immediately and even aggressive slags that would attack refractory materials to a high degree can be reliably granulated by the aid of propellant gases exhibiting substantially lower temperatures without involving the risk of the slag outlet opening of the tundish freezing, while, at the same time, enabling the desired solidification parameters to be varied within wide limits. To solve this object, the device according to the invention of the initially defined kind essentially consists in that the atomizer head is designed as a hot cyclone running into the cooling chamber, and that burners and/or propellant gas nozzles are connected to the hot cyclone. The use of a hot cyclone as an atomizer head avoids premature cooling in the region of the slag exit from the tundish, and hence the growing together of the tundish outlet as will be observed when blowing in a relatively cool propellant gas, whereby it is feasible in a particularly simple manner and with small structural dimensions to provide, within the cyclone atomizer head, the appropriate kinetic energy required to accelerate the particles, which enables subsequent rapid cooling and granulation even in short-structured devices. The hot cyclone designed as an atomizer head, moreover, allows for the adjustment of the respectively desired melt temperature, for instance, by arranging simple burners, which ensure the rapid formation of extremely small particles, and hence rapid cooling, upon emergence from the cyclone. In doing so, the slag melt may be kept away from the lining, for instance by forming a vapor cushion on the walls of the hot cyclone, and may be granulated to form solid slag particles, for instance by means of a wet vapor jet, the heat mass transfer in the hot cyclone proceeding particularly favorably. The cooling chamber, which is directly connected to the hot cyclone, may be an integral part of the cyclone and, in particular, a lower partial region of the cyclone and, via connections suitable to inject cooling agents, ensure the simple control of the cooling speed in altogether small-structured devices.

[0009] Advantageously, the configuration according to the invention is devised such that the axes of the propellant gas nozzles open tangentially to the axis of the hot cyclone, viewed axially, whereby the slag jet is imparted the appropriate kinetic energy to enable rapid circulation within the hot cyclone. Advantageously, the propellant gas nozzles in this case may be designed as slot nozzles extending in the axial direction of the jacket of the hot cyclone, whereby particularly favorable flow conditions will be obtained in that the clear widths of the slot nozzles taper in the direction towards the discharge opening of the hot cyclone. Basically, various media may be employed as propellants, whereby the respectively desired temperature may be maintained via additional burners. A suitable propellant preferably is a propellant vapor under a pressure of between 1.5 and 6 bars and at a temperature of between 200 and 800° C. such that expensive superheating of the vapor may be obviated.

[0010] In order to safeguard a rapidly circulating flow within the hot cyclone by means of such propellant gas jets, the configuration advantageously is devised such that the outlet opening of the melt tundish opens into the hot cyclone outside the axis of the same. A directed flow in the direction towards the cooling chamber in a simple manner may be achieved in that the axes of the propellant gas jets enclose an acute angle with the projection of the axis of the hot cyclone and extend in a downwardly oriented manner.

[0011] In principle, with the integration of the cooling chamber in the lower partial region of the cyclone, the configuration may be devised such that the discharge opening of the hot cyclone into the cooling chamber in terms of cross section corresponds to the clear cross section of the hot cyclone. If an additional acceleration of the peripheral speed is to be achieved in the lower partial region of the cyclone, the lower section may yet also comprise a conical runout region, the mouth into the consecutively provided cooling chamber consequently having a smaller clear cross section than the largest clear cross section of the hot cyclone.

[0012] By means of such a device, already pre-comminuted particles having a relatively high temperature will get into the cooling chamber, the subsequent control of the cooling speed being feasible by different, simple measures on account of the rapid heat mass transfer. It is, in particular, feasible to provide several cooling circuits and to connect to the cooling chamber nozzles for the injection of water, vapor and/or hydrocarbons, which are fed with the respective medium independently of one another in an accordingly controllable manner. When using hydrocarbons, a valuable burning gas is formed on account of the decomposition heat, or strongly endothermic cleavage into carbon monoxide and hydrogen, wherein carbon monoxide may subsequently even be reacted with water to CO₂ and H₂ if water or water vapor is injected. The burning gases formed may be immediately used further after a vapor condensation, particularly simple temperature control being feasible, in particular, by the addition of hydrocarbons.

[0013] In principle, it is advantageous if also the final granulate temperature can be adapted to the respective requirements. The final granulate temperature may advantageously be maintained at 300° to 500° C. over a period of 2 to 15 minutes, that maintenance of the final granulate temperature immediately leading to an activation of the slag. When using the end product in mixed cements, this will result in an enhanced early strength.

[0014] In order enable the suitable utilization of the burning gases formed during the injection of hydrocarbons, the configuration advantageously is devised such that a gas duct is connected to the hot cyclone or the cooling chamber to carry off hot gases such as, for instance, synthesis gas and/or burning gases. The off-gas formed may either be exploited energetically or used for pre-reduction or fine ore preheating or hot vapor recovering procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following, the invention will be explained in more detail by way of exemplary embodiments schematically illustrated in the drawing. Therein:

[0016]FIG. 1 is a partially sectioned diagrammatic view of an atomizer head according to the invention;

[0017]FIG. 2 is a view in the direction of the arrow II of FIG. 1;

[0018]FIG. 3 illustrates a modified embodiment of the atomizer head; and

[0019]FIG. 4 is a cross-sectional view of a further configuration of a hot cyclone atomizer head.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0020] From FIG. 1, a slag tundish 1 is apparent, whose outlet opening or mouth 20 is closeable by means of a slag flow control organ such as, e,.g., a height-adjustable stopper 2. The melt outlet opens into a hot cyclone 3 with the axis 4 of the mouth 20 being located eccentric relative to the axis 5 of the hot-air cyclone 3. A propellant such as, for instance, superheated vapor or wet vapor is blown in through a nozzle box 6, which causes an appropriate vapor layer to develop on the inner lining of the jacket of the hot cyclone 3 for the protection of the refractory lining of the hot cyclone 3. The slag jet 7 solidifies into extremely small particles 8 which are set in a rotary movement via the propellant nozzles in the hot cyclone. The cooling chamber 9, which is arranged to follow the hot cyclone, has conical walls so as to effect an additional acceleration of the rotary movement in that region. Cooling medium may be injected into this cooling chamber 9 via nozzles 10. If hydrocarbons are injected through nozzles 10, not only superheated vapor and fine dust, but also a burning gas formed by the reaction of hydrocarbons to CO and H₂ and a possible subsequent reaction of CO with H₂O to CO₂ and H₂ are drawn off through the central discharge duct 11.

[0021] In FIG. 2 the nozzle box is again denoted by 6, whereby the slag jet 7 in the instant case is diverted into peripherally extending paths 13 by the substantially tangentially oriented wet vapor nozzles 12, while solidifying at the same time. In FIG. 1, the discharge opening from the cooling chamber of the hot cyclone is designed as a cellular wheel sluice 14, whereby the hot granulates may be collected in a tub.

[0022] The individual nozzles 12 of FIG. 2, which may be arranged in several planes in the axial direction of the axis 5 of the hot cyclone, may be replaced with longitudinally slotted nozzles, a plurality of such nozzles being arrangeable in a peripherally distributed manner.

[0023] In the illustration according to FIG. 3, the melt tundish is again denoted by 1 and details of the hot cyclone 3 are more readily apparent. The nozzles, which are directed tangentially and downwardly in the direction of the axis, are again denoted by 12, wherein burners 14 are arranged coaxial with the axis 5 of the hot cyclone to maintain the temperature of the particles present in the hot cyclone at, for instance, 900 to 1500° C., at which temperature the particles enter the cooling chamber 9 arranged therebelow. Due to the high peripheral speed, the melt droplets leave the hot cyclone in a cone delimited by lines 15 as generatrices, while being braked off at the same time. Nozzles 16 and 17 open into the cooling chamber to enable the feeding of propellant vapor, cooling water or hydrocarbons in a separately controlled manner. Such a plurality of cooling circuits allows the cooling speed and the cooling characteristics to be controlled within wide limits.

[0024] Propellant vapor having a pressure of between 1.5 and 6 bars and a temperature of between 200 and 800° C. may be introduced through nozzles 12, whereby 100 to 600 kg vapor per ton of slag will be sufficient in the instant case to ensure the desired whirling and hence particle fineness within the hot cyclone 3. The slag melt may run down the wall of the hot cyclone 3 over a vapor cushion also in this embodiment, to which end wet vapor jets may be used, which granulate the slags to solid slag particles. In doing so, an extremely good heat mass transfer takes place within the hot cyclone 3, with the additionally formed vapor causing only a slight pressure loss. Overall, the hot cyclone may be designed to be extremely small-structured.

[0025] Unlike in the known configuration, the weir tube provided in the slag tundish 1 may, thus, be obviated, the control of the slag inflow being limited to the actuation of the stopper 3. Since no remarkable cooling occurs in the region of the mouth of the tundish, there is no risk of the melt freezing in the region of the mouth of the slag tundish, either. By an appropriate control of the supply of coolant through nozzles 16 and 17, also the final granulate temperature may be controlled to the desired extent.

[0026] In the configuration according to FIG. 4, in which a modified embodiment of the hot cyclone 3 is represented in section, a plurality of tangentially opening propellant gas nozzles 12 are designed as slot nozzles to be fed with a propellant medium and, in particular, propellant vapor from an annular space 18. The annular space 18 is delimited by an external wall 19 arranged concentric with the jacket of the hot cyclone 3.

[0027] As is apparent from FIG. 1, a screening wheel 21 may be arranged to separate extremely fine grains such that only extremely fine grains will be drawn off along with the gases.

[0028] Finally, in FIG. 5, the runout region 22 from the hot cyclone finally is designed to be itself conically such that the rotary movement is even further accelerated prior to the entry into the cooling chamber, thus enabling a further reduction of the droplet size. 

What I claim is:
 1. In a device for atomizing a melt, such as a liquid slag, of the type including a melt tundish having an outlet opening and intended to receive said melt, an atomizer head arranged in or on said outlet opening of said melt tundish and intended to produce an atomized melt, and a cooling chamber connected to said atomizer head and intended to receive said atomized melt, the improvement wherein said atomizer head is designed as a hot cyclone opening into said cooling chamber, and which further comprises at least one of burner means and propellant gas nozzle means connected to said hot cyclone.
 2. A device as set forth in claim 1, wherein said propellant gas nozzle means have propellant gas nozzle means axes and said hot cyclone has a hot cyclone axis, said propellant gas nozzle means axes extending tangentially to said hot cyclone axis, viewed axially.
 3. A device as set forth in claim 1, wherein said hot cyclone includes a hot cyclone jacket and said propellant gas nozzle means are designed as slot nozzles extending in the axial direction of said hot cyclone jacket.
 4. A device as set forth in claim 3, wherein said hot cyclone includes a discharge opening and said slot nozzles have clear width tapering towards said discharge opening of said hot cyclone.
 5. A device as set forth in claim 2, wherein said outlet opening of said melt tundish opens into said hot cyclone outside of said hot cyclone axis.
 6. A device as set forth in claim 2, wherein said propellant gas nozzle means axes enclose an acute angle with the projection of said hot cyclone axis and extend in a downwardly oriented manner.
 7. A device as set forth in claim 1, wherein said hot cyclone includes a discharge opening running into said cooling chamber and having a cross section corresponding to the clear cross section of said hot cyclone.
 8. A device as set forth in claim 1, wherein said hot cyclone includes a discharge opening running into said cooling chamber and having a conical runout region, said conical runout region having a clear cross section smaller than the clear cross section of said hot cyclone.
 9. A device as set forth in claim 1, wherein said hot cyclone is powered with a propellant gas having a temperature ranging between 200° and 800° C. and a pressure ranging between 1.5 and 6 bars.
 10. A device as set forth in claim 9, wherein said propellant gas is comprised of propellant vapor.
 11. A device as set forth in claim 1, further comprising further nozzle means connected to said cooling chamber to inject at least one of water, vapor and hydrocarbons.
 12. A device as set forth in claim 1, further comprising a gas duct connected to said hot cyclone to carry off hot gases.
 13. A device as set forth in claim 1, further comprising a gas duct connected to said cooling chamber to carry off hot gases.
 14. A device as set forth in claim 12, wherein said hot gases comprise at least one of synthesis gases and burning gases.
 15. A device as set forth in claim 13, wherein said hot gases comprise at least one of synthesis gases and burning gases. 